Communication using multiple transmitters and multiple receivers can be used to provide redundancy and thus to achieve reliability. Such systems also sometimes referred to as multiple input multiple output (MIMO) systems. Multiple spatially-diverse antennas have been used in wireless MIMO systems, and polarization can be used in optical MIMO systems to provide diversity and thus redundancy. Polarization diversity can address impairments in optical fiber such as cross-phase modulation (XPM) induced by polarization scattering, and also polarization-mode dispersion. Polarization diversity can also be used to address impairments in optical free-space communication, such as scattering and scintillatio. Polarization diversity uses multiple transmitters, each of which transmits using a different polarization state, thus transmitting redundant forms of the data to a receiver. The receiver can exploit the differences in the various received versions of the data to improve recovery of received data. However, conventional techniques employ multiple receivers as well as multiple transmitters, thus adding to the cost.